The present invention relates to an apparatus for closing and/or regulating the discharge or tapping of molten metal from a metallurgical vessel. More particularly, the present invention relates to such an apparatus including a refractory outer pipe member having therethrough a discharge passage defining outer and inner openings, and a refractory inner pipe member positioned within the outer pipe member, the inner pipe member having therethrough a discharge passage defining outer and inner openings. A first of the pipe members is movable, for example, rotatable or axially movable, with respect to a second of the pipe members between an opened position, whereat the discharge passages of the pipe members are aligned and with the inner opening of the outer pipe member confronting the outer opening of the inner pipe member, thereby defining a molten metal discharge channel that enables flow of molten metal through the pipe members in a flow direction from an inlet opening that receives molten metal from within the metallurgical vessel to an outlet opening to discharge the molten metal, and a closed position, whereat the discharge passages of the two pipe members are out of alignment and the inner opening of the outer pipe member and the outer opening of the inner pipe member are isolated from each other enclosed, thereby interrupting the discharge channel.
A closing and/or regulating apparatus of this general type is disclosed in German DE 37 31 600. In this type of device however, when the apparatus is in a closed position, molten metal will fill the discharge passage or passages through the outer pipe member but will not flow since the apparatus is closed. This molten metal can solidify or partially solidify within such discharge passage and form a solidified metal skin or small metal plug. Thereafter, when the movable pipe member is moved to the open position to open the apparatus, this frozen metal skin or metal plug can cause clogging of the molten metal discharge channel and prevent tapping of the molten metal. Thus, opening of the apparatus cannot be ensured 100 percent of the time, and this is an operational disadvantage.
In U.S. Pat. No. 3,511,471 there is disclosed a rotary slide gate or sliding closure unit having through various members discharge passages than can be aligned to form a discharge channel. The inlet opening to this discharge channel converges in a downstream direction. The result is that when the slide gate is in a closed position, a metal skin or metal plug that will form in the inlet discharge passage cannot be discharged with certainty upon subsequent opening of the apparatus. This is true even though this known slide gate discloses the downstream portions of the discharge channel diverge in a downstream direction.
Swiss Patent CH-PS 420,498 discloses a discharge apparatus where the relative position of a casting stream is changed by moving one member that partially forms a discharge channel. In this case, at least portions of the discharge channel converge in a downstream direction, and the above problem also occurs.